1. Field Of The Invention
The present invention relates generally to a method and apparatus for pultruding non-linear thermoplastic composite articles, and more particularly, to such a method and apparatus wherein angular bends are continuously formed in a pultruded thermoplastic composite.
2. Description Of The Prior Art
The production of molded thermoset resin products reinforced with a fibrous reinforcing material by the pultrusion process is well established. In such a pultrusion process, one or more reinforcing fiber strands are pulled from a creel, passed through a thermoset resin bath for impregnation thereby and then pulled through a heated composite forming die wherein the resin matrix is formed into a desired shape and cured. Various guide, preshaping and preheating mechanisms and apparatus are commonly utilized with and/or as a part of the heated forming die. The term "heated forming die" as hereinafter used is intended to be inclusive of such guide, preshaping and preheating apparatus. A pulling mechanism located after the heated forming die causes the composite to be forwarded through the process. Generally, the formed composite is cut into articles of determined length.
Pultrusion processes for producing reinforced composite products of thermoplastic material have also been developed and used heretofore. Such processes are similar to those for producing thermoset resin composite products described above except that the thermoplastic impregnated reinforcing material is pulled through a heated forming die or a heated forming die followed by a cooling die having temperatures such that the thermoplastic material is initially melted and shaped, and then cooled to a temperature whereby the thermoplastic material is substantially solidified.
Conventional pultrusion systems operate continuously to produce linear reinforced composite articles. That is, the composite formed is pulled through the heated forming die and other parts of the pultrusion system in a substantially linear path and cut into articles of selected length, i.e., articles having linear longitudinal axes.
U.S. Pat. No. 3,873,399 to Goldsworthy et al. issued Mar. 25, 1975, discloses a method and apparatus whereby pultruded reinforced thermoset resin composite articles are formed which are curved over at least a portion of their length. The method and apparatus involves the use of cooperating die sections which are arcuately curved over their length forming a die cavity therebetween.
U.S. Pat. No. 4,469,541 to Goldsworthy issued Sept. 4, 1984, discloses a pultrusion method for producing an arcuately shaped reinforced thermoset resin composite article. The method utilizes a die channel of varying cross-sectional shape to form reinforced composite articles with non-constant cross-sectional shape with or without constant cross-sectional volume. The longitudinal axes of the articles are either linear or arcuate.
U.S. Pat. Nos. 4,194,873 dated Mar. 25, 1980, 4,289,465 dated Sept. 15, 1980, and 4,296,060 dated Oct. 20, 1981 to Killmeyer et al. disclose pultruded continuous fiber reinforced composite articles of thermoset resin matrix having non-constant cross-sectional shapes and linear longitudinal axes.
By the present invention a method and apparatus for continuously pultruding non-linear reinforced thermoplastic composite articles having one or more angular or arcuate bends therein are provided.